This is the stuff that can turn your hair green I think, says about stains and chlorine on their site here: http://www.p20.co.uk/faqs/

I was in Turkey last year and we had a pool shared with about 10 people, all the blonde haired people had green tinted hair after a few days (also affected white parts of swimming costumes), spoke to a pool engineer whilst over there and apparently it's something that's in the P20 cream that reacts with chlorine.